铁基Heusler合金Fe2Co1-xCrxSi的结构、磁性和输运性质的研究

基于多种实验手段和能带计算的方法, 对四元合金Fe₂Co_1-xCr_xSi的晶体结构、 磁性、输运性质及能带结构进行了研究. 研究发现, 随着Cr的增加, 合金Fe₂Co_1-xCr_xSi保持了高度有序结构, 逐渐从Hg₂CuTi结构的Fe₂CoSi 过渡到L2₁结构的Fe₂CrSi; 由于次晶格网络的破坏, 居里温度逐渐下降; 系列合金的分子磁矩呈现线性下降, 符合半金属特性; 剩余电阻比率与原子占位有序程度密切相关, 呈现两端大、 中间小的特点. 在Cr替代Co的过程中, 材料半金属能隙逐渐打开, 表现半金属特征. 同时费米能级从Fe₂CoSi半金属能隙的价带顶上移至Fe₂CrSi能隙的导带底. 最大的能隙宽度出现在x= 0.75处, 这表明四元合金有可能成为具有更高自旋极化率和更强抗干扰能力的自旋电子学材料.

Structural, magnetic, transport, and half-metallic properties of Fe2Co1-xCrxSi Heusler alloys

The structural, the magnetic, the transport and the half-metallic properties of quaternary Heusler alloy Fe₂Co_1-xCr_xSi are investigated. The studies of X-ray diffraction and temperature dependence of magnetization reveal that Fe₂Co_1-xCr_xSi alloy always maintains a high degree of order, while the Curie temperature decreases gradually with the increase of Cr concentration x. Importantly, the lattice constant and the saturation magnetic moment of Fe₂Co_1-xCr_xSi alloy follow the Vegard law and half-metallic Slater-Pauling rule, respectively. Based on the band structure calculation, Fe₂Co_1-xCr_xSi alloy keeps a 100% spin polarization and Fermi level moves from the top of valence band to the bottom of conduction band, depending on Cr concentration x. Our results indicate that quaternary Fe₂Co_1-xCr_xSi Heusler alloy is a promising robust half-metallic candidate for spintronics applications.